Method of making magnetic alloys



- now largely used as a magnetic silicon iron for use as a ma Patented Jan. 19, 1926.

UNITED STATES PATENT oF icE.

ll'o Drawing.

To all whom it may concern:

Be it known that I, VERE B. BRowNE, a citizen of the United States, and a resident of Brackenridge, in the county of Allegheny and the State of Pennsylvania, have made a new and useful Invention in Methods of Making Magnetic Alloys, of which the following is a specification.

This invention relates to a method of manufacturing silicon iron.

Silicon iron or so called silicon steel is allo in the manufacture of certain parts of e ectrical apparatus on account of its high degree of magnetic permeability and low degree of magnetic hysteresis and this invention has particularly to do with the manufacture of etic alloy.

The highest grades of silicon iron now obtainable commercially have a silicon content. usually ranging from 3.5% to 4.5% and a carbon content ranging from .04% to..08%. It has been known for some time that the value of silicon iron as a ma netic alloy is not only determined by its silicon content but by its soundness and purity as well. Recent research on this subject as shown that carbon also plays an important part in the value of such material and that a sound earbonless silicon iron of the roper silicon content would have practica 1y no ma netic loss.

S mall laboratory quantities of silicon iron having an extremely low carbon content have been roduced in a vacuum furnace and b metliods which are wholly impractical or commercial production on a large scale.

In an application for United States Letters Patent filed by me, and serially numbered 16,837, I have disclosed a method of producing sound silicon iron alloys, that is, alloys that are-substantially free from slag and other solid inclusions such as silica.

An object of the invention of the present application'is to provide a method by means of which silicon iron having a silicon content such as is desirable in a magnetic alloy and a carbon content of not over .03% can be produced commercially and in large quantities.

A further object of this invention is to rovide a method by means of which silicon iron having a silicon content in excess of 3% and a carbon content of not over .03%

Application filed March 19, 1925. Serial K0. 16,838.

can be produced at a relatively low cost and in large quantities.

A still further object of this invention is to provide a method by means of which silicon iron free from sulphur and phosphorus and having a silicon content in excess of .5%, and a carbon content of not over .03% can be produced commercially and in large quantities.

These as well as other objects which will be a parent to those skilled in the art to wh1c this invention relates I attain by means of the method and the ste s thereof described in the specification an particularly set forth inthe claims forming part of this application for Letters Patent.

The method of this invention broadly consists in refining ironin afurnace and in removing from the molten iron as much carbon as is possible by standard methods,

then in passing air through the molten iron until all traces of carbon are removed and then in addin the desired amount of silicon to the carbon ree iron.

The iron may be refined in either an open hearth furnace or in an electric arc furnace. It is enerally more difficult to produce refined Iow carbon iron in an electric arc furnace than it is in an open hearth furnace, because carbon vapor iven off by the carbon HEISSUED electrodes in the arc urnace is absorbed by that practicing my invention I am able to utilize eitheran open hearth furnace or an electric arc furnace and that in either furnace I can produce an iron that is practically carbonless.

By adding to'this practically carbonless iron ferro silicon containing not over 2% of carbon I can produce silicon iron havin a carbon content not greater than .03% an at the same time having a silicon content as high as 5%.

In practicin the method of this invention 'I produce re ned iron in either an open the molten iron. I have found, however,

of" pipes into the bath and pass air through these to the bottom of, the bath. This air, upon issuing from these pipes, comes into intimate contact with all parts of the bath and oxidizes the remaining carbon.

These pipes will vary in size and number according to the size of the bath. They are preferably connected to a common header or line, which in turn is connected to a suitable source of air under pressure such as a blower or compressor. Where a cheap supply of oxygen is obtainable it is desirable to surcharge the air with oxygen and, of course, oxygen alone can be used with beneficial results. While it is not necessary to preheat the air this may be done if desired.

While as I have said the iron can be refined in either an open hearth or in an electric arc furnace, I prefer an electric arc furnace, since, in such a furnace, I can maintain a reducing atmosphere and therefore can eliminate all of the sulphur and phosphorus as well as the carbon. I do this by using progressive slags on the surface of the bath. I first use an oxidizing slag and thereby remove the phosphorus and a portion of the carbon. I then remove this slag and replace it by a reducin slag and thereby remove the sulphur. T e .reducing slag is then removed and replaced by another oxidizing slag. It is durin the period of this second oxidizing slag t at I introduce the air for oxidizing the remaining carbon.

' When the carbon has been removed I tap from the furnace a ladleful of this carbonless iron and make the silicon addition thereto. This is preferably done by placing in the ladle (before the molten carbonless lIOIl is tapped thereinto) the necessary amount of silicon to produce an alloy of the desired com osition. a

T e silicon is preferably added to the ladle in the form of ferro silicon and this is that produced electrically and is of thehighest grade obtainable and having a car- 7 bon content of not over 2%.

By using such ferro silicon I can obtain silicon iron having a silicon content ranging from 3.5% to 4.5% with a carbon content of not over .03%;

I have found that by this method I am able to produce silicon iron that is superior as a magnetic alloy to any heretofore produced commercially. It can be produced at a relatively low cost and in any quantity desired. I also find that I am able, at only a slight increase in cost over the present com mercial methods of manufacture, to obtain silicon iron having a silicon content as high as 4.5% and a carbon content that usually runs well below but never over .03%.

Having thus described my invention what I claim is:

.it for use as a magnetic alloy and a carbon content of not over .03%, which consists in refining iron, in reducing the carbon in the refined iron by making additions of iron ore to the bath until no further reduction of carbon is obtained by such additions, then in causing air or other oxidizing gas to permeate the bath until substantially all of the remaining carbon is removed, then in re- -moving metal from the bath and making the necessary silicon additions to the removed metal.

2. The method of making silicon iron having a silicon content sufficient to adapt it for use as a magnetic allo and a carbon content of not over 03%, w ich consists in refining iron in an open hearth or electric arc furnace, in reducing the carbon in the refined iron by making additions of iron ore t0 the bath until no further reduction of thereto until no further substantial reduction of carbon can be obtained by further additions, then in causing air or other oxidizin gas to permeate the bath until substantially all of the remaining carbon is removed, then in tapping metal from the furnace into ailadle and adding silicon to the metal 'in the ladle and then in casting such metal into in ots.

4. The method 0 making silicon iron having a silicon content sufficient to adapt it for use as a magnetic alloy and a relativel low carbon content, which consists in re ning iron in an open hearth or electric arc furnace, in reducing the carbon in the refined.

iron by adding iron ore thereto, in introducing air into the bottom of the bath in the furnace in sufficient quantity and for the necessary length of time to remove substantially all of the remaining carbon, in tapping metal from the furnace into a ladle I having a silicon content sufficient to ada t it for use as a magnetic alloy and a relative y low carbon content, which consists in refining a silicon content sufl'lcient to adapt it ing air into t e bottom of the bath in the furnace in sufficient quantity and for the necessary length of time to remove substantially all of the remaining carbon, in tapping metal from the furnace into a ladle and in adding thereto a sufficient quantity of ferro silicon having a carbon content of not over 2% to bring the silicon content of the finished alloy to at least 5% and then incasting such alloys into ingots.

6. The method of making silicon iron h?- or use as a magnetic allo and a relativel low carbon content, whic consists in re ning iron in an open hearth or electric arc furnace, in reducing the carbon in the refined iron by adding iron ore thereto, in introducing air into the bottom of the bath in the furnace in sufiicient quantity and for the necessary length of time to remove substantially all of the remaining carbon, in tapping metal from the furnace into a ladle and in adding thereto a suflicient quantity of ferro silicon having a carbon content of not over 2% to bring the silicon content of the finished allo to the point desired.

7. The metho of making silicon iron having asiliconcontent of at least 2% and a carbon content of not over .0370, which consists in refining iron in a reducing atmosphere and in utilizing an oxidizing slag to remove the sulphur and part of the carbon, in removing such slag and replacing the same by a reducing slag whereby the phosphorus is removed, in replacin the reducing slag by an oxidizing slag, t en in causing air or other oxidizing gas to permeate the bath until substantially all of the remaining carbon is removed, then in tapping metal'from the bath into a ladle and in making the necessary silicon addition to the metal in the ladle and then in casting the metal into ingots.

In testimony whereof, I have hereunto subscribed my name this 14th day of March,

1925. p VERE B. BROWNE. 

